1. Field of the Invention
The present invention relates to a thin film forming apparatus used for fabricating an EL element having a structure in which a luminescent material capable of generating EL (Electro Luminescence), particularly, a luminescent organic material (hereinafter referred to as organic EL material) is placed between an anode and a cathode.
2. Description of the Related Art
In recent years, a display device which uses an EL element as a self-luminous element using an EL phenomenon of an organic EL material (EL display device) has been developed. Since the EL display device is of a self-luminous type, a backlight as in a liquid crystal display device is not necessary. Further, since an angle of visibility is wide, the EL display device is regarded as promising as a display portion of a portable equipment used outdoors.
There are two kinds of EL display devices, that is, a passive type (simple matrix type) and an active type (active matrix type), and both types have been vigorously developed. Particularly, at present, the active matrix type EL display device has attracted a great deal of attention. With respect to the organic EL material which becomes a luminescent layer and can be regarded as the center of the EL element, although research has been made on a low molecular organic EL material and a high molecular organic EL material, attention has been paid to the high molecular organic EL material easier to handle and higher in heat resistance than the low molecular organic EL material.
As a film forming method of the high molecular organic EL material, an ink-jet method proposed by Seiko Epson Corporation has been regarded as promising. With respect to this technique, Japanese Patent Application Laid-open No. Hei. 10-12377, No. Hei. 10-153967 or No. Hei. 11-54270 may be referred to.
However, in the ink-jet method, since the high molecular EL material is jetted and is scattered, if a distance between a coated surface and a nozzle of a head for ink jet is not made suitable, there can occur a problem of a so-called flying curve in which a droplet falls to a portion other than a necessary portion. The flying curve is disclosed in detail in Japanese Patent Application Laid-open No. Hei. 11-54270, and it is specified that a deviation of 50 μm or more from an objective position can occur.